Sheet metal ducts or pipes having rolled beads at their ends are used in various industries, primarily for exhaust collection. The joining and sealing of pipe or duct joints is a critical concern. Proper sealing has become more important as efforts have increased to protect the environment. Liquid chemicals, mists, fumes, food and other materials, such as fine dust, must be conducted through pipelines without leakage of the material from the pipeline and without contamination from outside entering the pipeline. To seal the ends of a pipe or metal duct having rolled beads, installers typically have used a standard V-retainer coupling, the apex of the V-retainer coupling being flat.
For a good seal with a narrow coupling, the tolerances are low. A coupling having a flat apex wall requires an installer to estimate the midpoint of any cushion or gasket material in the coupling so that the midpoint of the gasket material is placed at the circumferential point of contact of the two pipe ends so that as much surface area of the cushion as possible is located on both sides of the pipe ends. Furthermore, a flat apex fails to urge the cushion towards the gap that is left between the two abutting edges of the pipes.
Accordingly there is a need for a coupling for joints between pipes having flanged ends, and more particularly, rolled beads at their ends where the coupling provides a superior seal and an aligning feature that facilitates assembly of the pipeline in field installations.